A method for preparing hydrophobic fluorescent carbon quantum dots from waste masks and hydrophobic fluorescent carbon quantum dots

Abstract

The application relates to the technical field of carbon quantum dots, in particular to a method for preparing hydrophobic fluorescent carbon quantum dots from waste masks and the hydrophobic fluorescent carbon quantum dots, and the method comprises the following steps: after ear bands and nose bridge strips of a waste medical mask are removed, a mask body is obtained; the mask body is placed in a container for high-temperature baking, and the mask body is taken out after cooling; the product after cooling is ground into powder, and a solvent is added for dispersion; the product after dispersion is subjected to dialysis purification and drying in sequence, and the hydrophobic fluorescent carbon quantum dots are obtained. The waste medical mask is prepared into the hydrophobic fluorescent carbon quantum dots through the high-temperature baking method, the waste mask is recycled, the carbon quantum dots can be used as hydrophobic materials, the quantum yield is higher, the preparation method is simple, the toxicity is low, and the environment is more friendly. The outer layer, the middle layer and the inner layer of the mask are treated respectively, three kinds of carbon quantum dots obtained have differences in hydrophobic performance and quantum yield, and the application range is wider.

Description

Technical Field

[0001] This invention relates to the field of carbon quantum dot technology, and in particular to a method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks, and the hydrophobic fluorescent carbon quantum dots themselves. Background Technology

[0002] The disposal of used face masks inevitably causes serious environmental pollution, and improper handling can lead to secondary pollution. Currently, the main method for disposing of used face masks is incineration, failing to utilize them and resulting in a severe waste of resources.

[0003] Carbon quantum dots are spherical fluorescent nanoparticles smaller than 10 nm, and have attracted widespread attention from scientists in recent years. If discarded face masks could be processed into carbon quantum dots, it would not only achieve waste utilization but also solve potential pollution problems. Common medical masks consist of three layers, inner and outer, with polypropylene as the main component. Technically, using polymers to prepare carbon quantum dots is relatively common. However, considering the large molecular weight and high thermal stability of the polymers used in mask preparation, conventional hydrothermal or microwave methods are not suitable for preparing carbon quantum dots. Summary of the Invention

[0004] The main objective of this invention is to provide a method for preparing hydrophobic fluorescent carbon quantum dots using discarded masks, and the hydrophobic fluorescent carbon quantum dots themselves. This aims to address the technical problem that existing methods, such as hydrothermal and microwave methods, are often used to prepare carbon quantum dots from discarded masks.

[0005] To achieve the above objectives, this invention proposes a method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks, comprising the following steps:

[0006] S1. After removing the ear loops and nose bridge strip from the discarded medical mask, the mask body is obtained;

[0007] S2. Place the cut mask body in a container and bake it at high temperature, then remove it after cooling;

[0008] S3. Grind the cooled product into powder, then add solvent to disperse it;

[0009] S4. The dispersed product is purified by dialysis and dried to obtain hydrophobic fluorescent carbon quantum dots.

[0010] The main material of discarded masks is polypropylene, with hydrophobic alkane groups at the chain ends. Utilizing this characteristic, discarded masks are used to prepare hydrophobic fluorescent carbon quantum dots. This method enables the reuse of discarded masks and converts them into high-value-added carbon quantum dot materials. These materials possess hydrophobic properties and can be used as hydrophobic materials. This scheme does not employ existing hydrothermal or microwave methods, but instead obtains carbon quantum dots with high quantum yield through high-temperature carbonization and baking of discarded masks. This method is simple to prepare, has low toxicity, and is more environmentally friendly. Discarded disposable medical masks are safely converted into valuable fluorescent carbon quantum dots through a simple process, achieving waste recycling. This has significant implications for the treatment of discarded disposable masks and subsequent research.

[0011] Preferably, the mask body includes an outer layer, a middle layer, and an inner layer, wherein the inner layer and the outer layer are both polypropylene spunbond fabric, and the middle layer is a polypropylene meltblown fabric layer;

[0012] In step S2, the outer layer, middle layer and inner layer of the mask are cut and placed in three containers for high-temperature baking, and then cooled.

[0013] In step S3, the cooled outer layer product, middle layer product, and inner layer product of the mask are ground into powder, and then solvents are added to disperse them respectively.

[0014] In step S4, the dispersed outer layer product, middle layer product, and inner layer product of the mask are sequentially purified by dialysis and dried to obtain the first hydrophobic fluorescent carbon quantum dot, the second hydrophobic fluorescent carbon quantum dot, and the third hydrophobic fluorescent carbon quantum dot.

[0015] Medical surgical masks typically consist of three layers, each primarily made of polypropylene, but with slight variations in molecular weight and composition. The outer and inner layers are made of polypropylene spunbond fabric, while the middle layer uses polypropylene meltblown fabric. Because the raw materials used in each layer of discarded masks differ, simultaneously cutting and baking all three layers at high temperatures would affect the properties of the resulting carbon quantum dots. For example, it would affect their hydrophilicity and hydrophobicity; mixing highly hydrophilic and hydrophobic carbon quantum dots would reduce their performance. Therefore, this solution processes the outer, middle, and inner layers of the mask separately. After high-temperature baking, grinding, dispersion, dialysis purification, and drying, three types of hydrophobic fluorescent carbon quantum dots are obtained: a first type, a second type, and a third type. These three types of carbon quantum dots exhibit different hydrophobic properties and quantum yields, resulting in a wider range of applications.

[0016] Preferably, in step S2, the high-temperature baking temperature is 100℃-400℃, and the baking time is 1-10 hours. Within the above-mentioned high-temperature baking temperature and time range, waste medical masks can be converted into carbon quantum dots with the required performance. The above-mentioned high-temperature baking temperature actually refers to the maximum baking temperature, which is gradually increased from room temperature to this temperature.

[0017] Preferably, the high-temperature baking process in step S2 includes the following steps: First stage: heating from room temperature to 200℃ at a heating rate of 5-8℃ / min, holding at this temperature for 10-20 minutes; Second stage: heating from 200℃ to 260℃ at a heating rate of 10-15℃ / min, holding at this temperature for 15-40 minutes; Third stage: heating from 260℃ to 300℃ at a heating rate of 2-4℃ / min, holding at this temperature for 40-180 minutes. The room temperature referred to in this scheme is approximately 20℃.

[0018] The three baking stages mentioned above represent more suitable baking parameters for discarded medical masks. Under the baking temperature and baking time of the different stages, the quantum yield of carbon quantum dots is higher and the hydrophobic properties are better. In addition, the heating rate during high-temperature baking is further limited, and the process of converting discarded medical masks into carbon quantum dots is reasonably controlled, which further improves the quantum yield and hydrophobic properties of carbon quantum dots.

[0019] Preferably, in step S4, the molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, and the dialysis purification time is 8-24 hours. After dialysis purification, impurities of non-carbon quantum dots obtained after high-temperature baking can be removed. In this scheme, the molecular weight cutoff of the dialysis bag is about 1000-3000, and the size of the carbon quantum dots obtained after dialysis purification is about 10 nm.

[0020] Preferably, in step S4, the drying temperature is 50-120℃, and the drying time is 1-5 hours. The drying process is mainly used to remove moisture from the carbon quantum dots after dialysis purification.

[0021] Preferably, in step S3, the solvent used for dispersion is at least one of methanol, ethanol, propanol, isopropanol, acetone, ethyl acetate, or n-hexane.

[0022] In addition, this invention proposes a hydrophobic fluorescent carbon quantum dot, prepared by the method described above for preparing hydrophobic fluorescent carbon quantum dots using discarded masks. This hydrophobic fluorescent carbon quantum dot, due to the use of the aforementioned method for preparing hydrophobic fluorescent carbon quantum dots using discarded masks, possesses the beneficial effects of the methods described above, which will not be elaborated further here.

[0023] Preferably, the contact angle of the first hydrophobic fluorescent carbon quantum dot is 110-130°, the contact angle of the second hydrophobic fluorescent carbon quantum dot is 90-140°, and the contact angle of the third hydrophobic fluorescent carbon quantum dot is 80-120°.

[0024] Compared with existing technologies, the method for preparing hydrophobic fluorescent carbon quantum dots from discarded masks and the hydrophobic fluorescent carbon quantum dots of the present invention have the following beneficial effects: Hydrophobic fluorescent carbon quantum dots are prepared from discarded medical masks using a high-temperature baking method, realizing the reuse of discarded masks and converting them into high-value-added carbon quantum dot materials that can be used as hydrophobic materials. This preparation process is relatively simple, has low toxicity, and is more environmentally friendly, achieving waste recycling. Specifically, this method involves subjecting the outer, middle, and inner layers of the mask to high-temperature baking, grinding, dispersion, dialysis purification, and drying, respectively, to obtain first, second, and third hydrophobic fluorescent carbon quantum dots. Due to the special high-temperature baking process, the obtained carbon quantum dots have a higher quantum yield and stable hydrophobicity. Furthermore, the three types of carbon quantum dots differ in hydrophobic properties and quantum yield, resulting in a wider range of applications and scenarios for the obtained carbon quantum dots. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 Photographs showing the preparation of carbon quantum dots in the inner layer, middle layer, and outer layer of the mask in Embodiment 2 of this application;

[0027] Figure 2 The emission spectra of three different carbon quantum dots obtained in the inner layer, middle layer and outer layer of the mask in Embodiment 2 of this application at different excitation wavelengths are shown.

[0028] Figure 3 Infrared spectra of three different carbon quantum dots obtained in the inner layer, middle layer and outer layer of the mask in Embodiment 2 of this application;

[0029] Figure 4 This is a photograph of the contact angle of carbon quantum dots obtained in the inner layer of the mask in Embodiment 2 of this application;

[0030] Figure 5 This is a photograph of the contact angle of carbon quantum dots obtained in the middle layer of the mask in Embodiment 2 of this application;

[0031] Figure 6 This is a photograph of the contact angle of carbon quantum dots obtained from the outer layer of the mask in Embodiment 2 of this application.

[0032] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] Furthermore, the technical solutions of the various embodiments can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0035] A method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks includes the following steps:

[0036] S1. After removing the ear loops and nose bridge strip of the discarded medical mask, the mask body is obtained; the mask body includes an outer layer, a middle layer and an inner layer, wherein the inner layer is a non-woven fabric layer, and the outer layer and the middle layer are both polypropylene meltblown fabric layers.

[0037] S2. After cutting the outer layer, middle layer and inner layer of the mask, place them in three containers for high-temperature baking, and then cool them.

[0038] The high-temperature baking temperature is 100℃-400℃, and the baking time is 1-10h;

[0039] Specifically, the high-temperature baking process includes the following steps: First stage: heating from room temperature to 200℃ at a heating rate of 5-8℃ / min, and holding at that temperature for 10-20 minutes; Second stage: heating from 200℃ to 260℃ at a heating rate of 10-15℃ / min, and holding at that temperature for 15-40 minutes; Third stage: heating from 260℃ to 300℃ at a heating rate of 2-4℃ / min, and holding at that temperature for 40-180 minutes.

[0040] S3. Grind the cooled outer layer product, middle layer product, and inner layer product of the mask into powder respectively, and then add solvent to disperse them respectively. The solvent used for dispersion is at least one of methanol, ethanol, propanol, isopropanol, acetone, ethyl acetate, or n-hexane.

[0041] S4. The dispersed outer layer product, middle layer product, and inner layer product of the mask are sequentially subjected to dialysis purification and drying to obtain the first hydrophobic fluorescent carbon quantum dots, the second hydrophobic fluorescent carbon quantum dots, and the third hydrophobic fluorescent carbon quantum dots. The molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, the dialysis purification time is 8-24h, the drying temperature is 50-120℃, and the drying time is 1-5h.

[0042] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] A method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks includes the following steps:

[0045] S1. After removing the ear loops and nose bridge strip of the discarded medical mask, the mask body is obtained; the mask body includes an outer layer, a middle layer and an inner layer, wherein the inner layer is a non-woven fabric layer, and the outer layer and the middle layer are both polypropylene meltblown fabric layers.

[0046] S2. Cut the outer layer, middle layer and inner layer of the mask and place them in a container to mix. Bake at high temperature and then cool. During the high temperature baking, the temperature is increased from room temperature to 250℃ at a constant rate of 20℃ / min, and baked (held) at 250℃ for 2 hours.

[0047] S3. Grind the cooled mask (body) product into powder, and then add n-hexane solvent to disperse it;

[0048] S4. After the dispersed mask (body) product is purified by dialysis and dried, hydrophobic fluorescent carbon quantum dots are obtained. The molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, the dialysis purification time is 18h, the drying temperature is 100℃, and the drying time is 2h.

[0049] The carbon quantum dots prepared in Example 1 were subjected to performance testing, and the test results are shown in the table below:

[0050] Quantum yield Contact angle Example 1 9.8％ 118°

[0051] The test results from Example 1 show that only one type of carbon quantum dots can be obtained by mixing the outer, middle, and inner layers of the mask and then subjecting them to high-temperature carbonization processes. Combined with data from multiple experiments, it can be concluded that the quantum yield of carbon quantum dots obtained by mixing the outer, middle, and inner layers of the mask is 1-12%, and the contact angle is 100-130°.

[0052] Example 2

[0053] A method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks includes the following steps:

[0054] S1. After removing the ear loops and nose bridge strip of the discarded medical mask, the mask body is obtained; the mask body includes an outer layer, a middle layer and an inner layer, wherein the inner layer and the outer layer are both polypropylene spunbond fabric, and the middle layer is a polypropylene meltblown fabric layer;

[0055] S2. The outer layer, middle layer and inner layer of the mask are cut and placed in three containers for high-temperature baking, and then cooled; wherein, during high-temperature baking, the temperature is uniformly increased from room temperature to 250°C at a heating rate of 20°C / min, and baked (held) at 250°C for 2 hours.

[0056] S3. Grind the cooled outer layer product, middle layer product, and inner layer product of the mask into powder respectively, and then add n-hexane solvent to disperse them respectively;

[0057] S4. The dispersed outer layer product, middle layer product, and inner layer product of the mask are sequentially subjected to dialysis purification and drying to obtain the first hydrophobic fluorescent carbon quantum dots, the second hydrophobic fluorescent carbon quantum dots, and the third hydrophobic fluorescent carbon quantum dots. The molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, the dialysis purification time is 18h, the drying temperature is 100℃, and the drying time is 2h.

[0058] Example 3

[0059] A method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks includes the following steps:

[0060] S1. After removing the ear loops and nose bridge strip of the discarded medical mask, the mask body is obtained; the mask body includes an outer layer, a middle layer and an inner layer, wherein the inner layer and the outer layer are both polypropylene spunbond fabric, and the middle layer is a polypropylene meltblown fabric layer;

[0061] S2. The outer layer, middle layer and inner layer of the mask are cut and placed in three containers for high-temperature baking, and then cooled; wherein, during high-temperature baking, the temperature is uniformly increased from room temperature to 200°C at a heating rate of 20°C / min, and baked (held) at 200°C for 2 hours.

[0062] S3. Grind the cooled outer layer product, middle layer product, and inner layer product of the mask into powder respectively, and then add ethanol solvent to disperse them respectively;

[0063] S4. The dispersed outer layer product, middle layer product, and inner layer product of the mask are sequentially subjected to dialysis purification and drying to obtain the first hydrophobic fluorescent carbon quantum dots, the second hydrophobic fluorescent carbon quantum dots, and the third hydrophobic fluorescent carbon quantum dots. The molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, the dialysis purification time is 20 hours, the drying temperature is 85°C, and the drying time is 3 hours.

[0064] Example 4

[0065] A method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks includes the following steps:

[0066] S1. After removing the ear loops and nose bridge strip of the discarded medical mask, the mask body is obtained; the mask body includes an outer layer, a middle layer and an inner layer, wherein the inner layer and the outer layer are both polypropylene spunbond fabric, and the middle layer is a polypropylene meltblown fabric layer;

[0067] S2. The outer layer, middle layer and inner layer of the mask are cut and placed in three containers for high-temperature baking, and then cooled; wherein, during high-temperature baking, the temperature is uniformly increased from room temperature to 300°C at a heating rate of 15°C / min, and baked (held) at 300°C for 2.5 hours.

[0068] S3. Grind the cooled outer layer product, middle layer product, and inner layer product of the mask into powder respectively, and then add n-hexane solvent to disperse them respectively;

[0069] S4. The dispersed outer layer product, middle layer product, and inner layer product of the mask are sequentially subjected to dialysis purification and drying to obtain the first hydrophobic fluorescent carbon quantum dots, the second hydrophobic fluorescent carbon quantum dots, and the third hydrophobic fluorescent carbon quantum dots. The molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, the dialysis purification time is 15h, the drying temperature is 110℃, and the drying time is 2.5h.

[0070] The carbon quantum dots prepared in Examples 2-4 above were subjected to performance testing, and the test results are shown in the table below:

[0071]

[0072] Note: High molecular weight polymers, especially those with very high molecular weights like those used in face masks, are difficult to convert into carbon dots with high quantum yield. Traditional methods for preparing carbon quantum dots include microwave and hydrothermal methods, but neither of these methods can successfully convert waste face masks into carbon dots. Therefore, this solution uses high-temperature baking to prepare carbon quantum dots.

[0073] As shown in the test results in the table above, as in Examples 2-4, this method, by treating the outer layer, middle layer, and inner layer of the mask separately, can obtain three different types of carbon quantum dots: a first hydrophobic fluorescent carbon quantum dot, a second hydrophobic fluorescent carbon quantum dot, and a third hydrophobic fluorescent carbon quantum dot. Based on multiple experimental test data, the contact angles of the first, second, and third hydrophobic fluorescent carbon quantum dots are 110-130°, 90-140°, and 80-120°, respectively. All three exhibit good hydrophobic effects, but there are differences in the hydrophobicity among the various carbon quantum dots. Similarly, the quantum yields of the three different carbon quantum dots (first, second, and third) can reach over 2%, 1%, and 3%, respectively.

[0074] In particular, the optimal conditions for preparing carbon quantum dots in each layer of the mask according to this scheme are a baking temperature of 250℃ (heating at a uniform rate of 20℃ / min) and a baking (holding) time of 2h. Since the temperature is closely related to the carbonization of organic matter, the degree of carbonization is too low or too high, which will determine the size of fluorescence. When the baking parameters are limited to the above range, the quantum yield of carbon quantum dots is high and the hydrophobic properties are good.

[0075] Example 5

[0076] The preparation steps and parameters in this embodiment are the same as in Example 2, except that the parameters during high-temperature baking are different, as detailed in the table below:

[0077]

[0078] The hydrophobic fluorescent carbon quantum dots prepared in Example 5 above were subjected to performance testing, and the test results are shown in the table below:

[0079]

[0080] The test results from Examples 1 and 5 show that the carbon quantum dots obtained by using the special three-stage high-temperature baking process of this scheme have better performance than those obtained by uniformly heating to the rated temperature and then holding for a period of time. Combined with the test data from multiple experiments with different parameters, it can be determined that by using the special three-stage high-temperature baking process of this scheme, the quantum yield of the inner layer of the mask can be maintained above 11%, the quantum yield of the middle layer of the mask can be maintained above 7%, and the quantum yield of the outer layer of the mask can be maintained above 12%. Furthermore, the carbon quantum dots obtained have a smaller contact angle difference and more stable hydrophobicity.

[0081] More preferably, the high-temperature baking process of this solution is limited to the following stages: a first stage: heating from room temperature to 200°C at a heating rate of 6.2-7°C / min and holding for 10-15 min; a second stage: heating from 200°C to 260°C at a heating rate of 12-13.5°C / min and holding for 20-30 min; and a third stage: heating from 260°C to 300°C at a heating rate of 3-4°C / min and holding for 150-180 min. Within the above-mentioned more preferred ranges, the quantum yield of the inner layer of the mask can be maintained at over 12%, the quantum yield of the middle layer of the mask can be maintained at over 8%, and the quantum yield of the outer layer of the mask can be maintained at over 13%.

[0082] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing hydrophobic fluorescent carbon quantum dots using discarded face masks, characterized in that, Includes the following steps: S1. After removing the ear loops and nose bridge strip of the discarded medical mask, the mask body is obtained; the mask body includes an outer layer, a middle layer and an inner layer, wherein the inner layer and the outer layer are both polypropylene spunbond fabric, and the middle layer is a polypropylene meltblown fabric layer; S2. The outer layer, middle layer, and inner layer of the mask are cut and placed in three separate containers for high-temperature baking, followed by cooling. During the high-temperature baking, the first stage involves heating from room temperature to 200°C at a rate of 7°C / min and holding for 13 minutes; the second stage involves heating from 200°C to 260°C at a rate of 13.5°C / min and holding for 25 minutes; the third stage involves heating from 260°C to 300°C at a rate of 4°C / min and holding for 160 minutes. S3. Grind the cooled outer layer product, middle layer product, and inner layer product of the mask into powder respectively, and then add n-hexane solvent to disperse them respectively; S4. The dispersed outer layer product, middle layer product, and inner layer product of the mask are sequentially subjected to dialysis purification and drying to obtain the first hydrophobic fluorescent carbon quantum dots, the second hydrophobic fluorescent carbon quantum dots, and the third hydrophobic fluorescent carbon quantum dots. The molecular weight cutoff of the dialysis bag during dialysis purification is 1000-3000, the dialysis purification time is 18h, the drying temperature is 100℃, and the drying time is 2h.

2. A hydrophobic fluorescent carbon quantum dot, characterized in that, It is prepared by the method for preparing hydrophobic fluorescent carbon quantum dots using discarded masks as described in claim 1.

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